Bridget the lioness has a unique trait that most other lionesses do not have - she has a mane. Zoologists are still baffled as to why she just suddenly grew one. ( Oklahoma City Zoo | Twitter )

The lion's signature mane is normally reserved for the males, but Oklahoma City Zoo's lioness, Bridget, surprised zoologists when she started developing a mane last year. So far, zoologists are still trying to understand the curious case of Bridget's mini mane.

Bridget The Lioness' Surprise

Last year, Oklahoma City Zoo's 18-year-old African lioness suddenly began growing a mini mane quite similar to the ones in males as a result of increased testosterone. It all began around March of 2017 when her caretakers noticed the extra fluff of hair around her neck and head.

"After a while, it became obvious to everybody that Bridget was developing something a little different," said associate veterinarian of the zoo, Gretchen Cole, in an interview.

Despite the rare change in her, the carers state that Bridget does not seem to notice the extra growth of her hair. She eats and acts normally, and maintains her "strong attitude." Further, the zoo staff members are continuously watching her closely, though the extra growth is not expected to negatively affect her quality of life.

Rare But Not Unheard Of

Typically, males develop their manes at about one-year-old when their testosterone levels increase. In females, however, the development of manes is pretty rare though not unheard of. According to the Association of Zoos and Aquariums (AZA), experts have previously seen this phenomenon in female lions.

In 2011, a 13-year-old lioness at a zoo in Africa also developed a mane just like Bridget's when her ovary issue resulted in the development of excess testosterone production. However, the mane receded when it was finally resolved. Just a few years later in 2014, a group of five wild lionesses in Botswana were also observed to have manes and engaged in masculine behavior. However, because they seem to have developed it early on, experts believe that the cause is likely genetic.

Bridget's Curious Case

In the case of Bridget, however, experts have yet to discover the cause of the sudden mane growth. So far, experts have successfully drawn blood samples from her tail without having to use an anesthesia, and are currently awaiting results.

It's possible that genetics might be the cause of the mane growth, but her sister, 18-year-old Tia, did not grow a mane. Furthermore, experts believe that another possible cause might be a tumor located somewhere in her pituitary or adrenal gland.